Tunnel burners



Sept. 27, 1966 T. WARD TUNNEL BURNERS Filed July 1, 1964 INVENTOR TREVOR A4920 BY 1 g ATTORNEYs United States Patent 3,275,057 TUNNEL BURNERS Trevor Ward, Dewsbury, England, assignor to Hotwork Limited, London, England Filed July 1, 1964, Ser. No. 379,522 'SClaims. (Cl. 158-11) This invention relates to tunnel burners for providing a high velocity stream of hot gas to be used for heating purposes, such as, for example, the warming up of glass melting furnaces after shut-down.

It is the main object of the invention to provide a tunnel burner in which the temperature of the gas may be varied within wide limits by very simple control means.

It is another object of the invention to provide a tunnel burner of light weight and simple construction.

According to the present invention in a tunnel burner using gaseous fuel the gas is supplied separately from the combustion air to the combustion zone, the said gas and air being supplied in such a way that separate streams thereof, at least one of which is turbulent, merge together in the said combustion zone. Such merging of the streams produces a random mixing of the gas and air which, regardless of the overall proportions of said media, provides at some points a mixture in optimum proportions for combustion, and thereby ensures continuous combustion.

Preferably the gas enters the combustion zone through an annular orifice between a central air passage and an annular external air passage, so that combustion tends to take place in a region spaced inwardly from the tunnel wall and the said wall is protected from excessive heating.

The annular orifice through which the gas enters the combustion zone may be restricted by an annular flange protruding from one of its bounding walls, to increase the turbulence of the issuing stream of gas.

The invention is hereinafter described with reference to the accompanying drawings, in which:

FIGURE 1 is a longitudinal section through one form of tunnel burner according to the invention; and

FIGURE 2 is a partial section on an enlarged scale showing how the burner operates.

Referring to the drawings, a tubular casing of stainless steel has its largest diameter portion at 11 from which a convergent portion 12 leads towards a cylindrical outlet nozzle 13; The casing 10 also decreases in diameter towards its other end, where it is connected by an elbow 14 to an air duct 15 through which air can be blown into the casing by a fan (not shown). the flow of air being controlled by a butterfly valve 16 or by other convenient means.

A transverse partition 17 mounted in the largest diameter portion 11 of the casing supports two concentric tubes 18 and 19 projecting into the convergent portion 12, the outer tube 18 being longer than the inner tube 19 and the said tubes being provided at their forward ends with outwardly projecting flanges 21 and 22 respectively.

The inner tube 19 surrounds a central opening 23 in the partition 17, a circular series of orifices 24 in the said partition provide communication between the space behind the partition and the annular space around the outer tube 18, and a conduit 25 extending through the casing from an elbow fitting 26 passing through the wall of the said casing, leads by way of an orifice 27 in the partition into the annular space between the tubes 18 and 19. The conduit 25 serves as a main combustible gas supply conduit for the burner, and another conduit 28 of smaller bore, shown in FIGURE 1 and also connected to the annular space between the tubes 18 and 19, provides a pilot gas supply.

A tubular oil burner 29, which may be retractable, ex-

ice

tends through the opening 23, the said burner comprising an oil supply conduit 31 connected by flexible tubing '32 to an oil supply source (not shown) and a surrounding air tube 33 connected by means of flexible tubing 34 to 'a'sour'ce of compressed air (not shown).

The combustion chamber 35 of the burner is constituted by the interior of the convergent portion 12 of the burner casing, and it will be apparent that air will flow into the' said chamber both through the bore of the tube 19 and through the annular space between the outer tube 18 and the casing. Gas will flow into the said chamber through the annular space between the tubes 18 and 19. The flow of gas is obstructed by the radial flange 22, and the flow of air between the outer tube 18 and the casing is obstructed by the flange 21, so that convergent annular regions of comparatively low pressure are created in the. combustion chamber on the downstream side of the flanges, and eddies of gas and air from the main streams enter these regions and mix together, giving a random mixture in the region indicated by the dotted lines at 36 in FIGURE 2, which mixture, at some points at least, is at or near the optimum for combustion, so that combustion is maintained steadily and is not affected by quite wide variations in the proportions of gas and air supplied to the burner. Thus the said proportions can be widely varied to vary the temperature of the burner gases.

Ignition of the gas is effected by a sparking plug 37 which, as shown in FIGURE 1, is mounted in the par-tition 17 in the space between the tubes 18 and 19.

The oil burner 29 is used when higher heat inputs are required than can be obtained by burning gas alone, the burner 29 then being projected into the combustion chamber if it is retractable and oil being supplied to it.

The combustion gases form a convergent annular stream indicated at 38 in FIGURE 2, and the annular stream of air which passes outside the outer tube 18 surrounds the said stream 38 and tends to shield the casing 12 from the highest temperatures in the combustion chamber, so that the said casing 12 remains comparatively cool and no refractory lining is necessary. This enables the size of the burner to be substantially reduced as compared with known burners of the same general type, and reduces the cost of manufacture as well as increasing the portability and adaptability of the burners.

It will be understood that the obstruction of the flow of gas and air past the tubes 18 and 19 may be produced by means other than the flanges 21 and 22. For example, similar flanges may be provided projecting inwardly from the tubes, or other flow obstructing devices may be provided.

I claim:

1. A tunnel burner using gaseous fuel, said burner comprising a casing forming a generally conical combustion zone tapered toward an open end of the casing, said end constituting a nozzle for discharging the products of combustion in the burner, 21 pair of concentrically disposed tubes mounted in said conical combustion zone parallel to the center axis thereof, said tubes defining an annular inner space between each other and an annular outer space between the outer one of said tubes and the casing wall, a first feed means for directing a flow of gaseous fuel through said inner annular space into said combustion zone, a second feed means for directing a flow of air through said outer annular space and the inner one of said tubes into said combustion zone, and flow-deflecting means at the flow discharge end of the inner one of said tubes, said deflecting means deflecting the flow of gaseous fuel toward the inner wall of the outer tube, thereby creating a turbulence in the flow of gaseous fuel entering the combustion zone.

2. A tunnel burner according to claim 1, wherein said flow-deflecting means comprises an outwardly directed annular flange extending from the inner one of said tubes. 7 3. A tunnel-burner according to claim '1 and comprising second fiow-deflecting means at the discharge end .of

- 5. A tunnel burner according to claim 1 and comprising anoil-burning booster burner including a burner tube extending through the inner one of said tubes into said combustion zone.

References Cited by the Examiner UNITED STATES PATENTS 2,360,548 10/1944 Conway 158-110 X 2,458,542 1/1949 Urquhart 158 1 l 3,195,606 7/l965' Stout l5811 X FREDERICK L. MATIESQN, 111., Primary Exaniiner.

E. G. FAVORS, Assistant Examiner. 

1. A TUNNEL BURNER USING GASEOUS FUEL, SAID BURNER COMPRISING A CASING FORMING A GENERALLY CONICAL COMBUSTION ZONE TAPERED TOWARD AN OPEN END OF THE CASING, SAID END CONSTITUTING A NOZZLE FOR DISCHARGING THE PRODUCTS OF COMBUSTION IN THE BURNER, A PAIR OF CONCENTRICALLY DISPOSED TUBES MOUNTED IN SAID CONICAL COMBUSTION ZONE PARALLEL TO THE CENTER AXIS THEREOF, SAID TUBES DEFINING AN ANNULAR INNER SPACE BETWEEN EACH OTHER AND AN ANNULAR OUTER SPACE BETWEEN THE OUTER ONE OF SAID TUBES AND THE CASING WALL, A FIRST FEED MEANS FOR DIRECTING A FLOW OF GASEOUS FUEL THROUGH SAID INNER ANNULAR SPACE INTO SAID COMBUSTION ZONE, A SECOND FEED MEANS FOR DIRECTING A FLOW OF AIR THROUGH SAID OUTER ANNULAR SPACE AND THE INNER ONE OF SAID TUBES INTO SAID COMBUSTION ZONE, AND FLOW-DEFLECTING MEANS AT THE FLOW DISCHARGE END OF THE INNER ONE OF SAID TUBES, SAID DEFLECTING MEANS DEFLECTING THE FLOW OF GASEOUS FUEL TOWARD THE INNER WALL OF THE OUTER TUBE, THEREBY CREATING A TURBULENCE IN THE FLOW OF GASEOUS FUEL ENTERING THE COMBUSTION ZONE. 